1. Technical Field
The present invention relates to a piezoelectric element, a piezoelectric actuator, a liquid ejecting head, and a liquid ejecting apparatus.
2. Related Art
Piezoelectric elements are deformed according to the voltage applied thereto, and have a structure in which a piezoelectric layer is disposed between electrodes. Piezoelectric elements are used in liquid ejecting heads of ink jet printers, and other various devices such as actuators.
The piezoelectric layer of the piezoelectric element is liable to be degraded by moisture or the like. In order to prevent the degradation of the piezoelectric layer caused by moisture from the atmosphere, for example, the ink jet recording head disclosed in JP-A-10-226071 is provided with a protective film over the side surfaces of the piezoelectric layer and the upper surface of the lower electrode.
In order to enhance the reliability of the piezoelectric element having such a structure, it is important to enhance the adhesion between the protective film and each of the piezoelectric layer and the lower electrode. If the lower electrode is made of a noble metal, such as platinum (Pt) or iridium (Ir), the adhesion between the lower electrode and the protective film is reduced because these metals are not reactive. If the adhesion between the protective film and the piezoelectric layer or the lower electrode is insufficient, the protective film may be removed from the piezoelectric layer or the lower electrode, or may separate to form a space between the protective film and the piezoelectric layer or lower electrode. Such removal or separation causes a defect in the protective film, and consequently, the protective film cannot maintain its function as a barrier. Thus, the reliability of the piezoelectric element may be reduced.